Acute Coronary Syndrome (ACS)

by Khalid Mohammed Ali, Shirley Ooi – Singapore

Case Presentation

A 46 years old man with a past medical history of hypertension and hyperlipidemia developed central crushing chest pain associated with sweating and shortness of breath while driving. He presented to the emergency department 1 hour after the onset of chest pain. On physical examination, his vital signs were as follows; pulse rate: 60 beats/min, blood pressure: 100/50 mm Hg, respiratory rate: 20/min, SpO2 98% on room air. Patient has no leg edema, new murmur or features of heart failure.

His ECG is as follows:

What are the ECG features? What is the diagnosis?

Answer

ECG features are ST elevation more than 2 mm in inferior leads (II, III, AVF) with reciprocal changes (deep ST depression in lateral leads of I, AVL) and ST depression in lead V1, V2 which indicate the involvement of posterior wall.
The ECG is diagnostic of inferior and posterior wall ST elevation MI.

History and Physical Examination Hints

Chest pain described as pressure, squeezing or a burning sensation across the precordium and may radiate to the neck, shoulder, jaw, back, upper abdomen, or either or both arms.

Shortness of breath especially exertional dyspnoea

Palpitation

Diaphoresis from sympathetic stimulation

Nausea from vagal stimulation

Decreased effort tolerance

It is important to ascertain the onset of chest pain as it will affect the management of STEMI. Other important questions to ask are the chest pain character, radiation, associated symptoms, relieving and exacerbating factors, especially exertion.

Do not forget to ask about the risk factors. You can use the TIMI score.

TIMI (Thrombolysis in Myocardial Infarction) investigators have developed a 7-variable risk stratification tool that predicts the risk of death, re-infarction, or urgent revascularization at 14 days after the presentation:

≥ 65 years of age

Presence of ≥ three cardiac risk factors

Prior coronary artery stenosis of ≥ 50%

>= two angina events in the preceding 24 hours

Aspirin use in the previous seven days

ST-segment deviations of ≥ 0.5 mm on ECG at presentation

Positive cardiac biomarkers

Patients are considered to be high risk if their TIMI risk score is ≥ 5 and low risk if the score is ≤ 2. High-risk patients have a more significant benefit from early percutaneous coronary intervention and use of adenosine phosphate inhibitor and low molecular weight heparin than lower risk patients.

Most of the cases with ACS have a normal cardiovascular examination. In a busy emergency department where time is of an essence, targeted physical examination in the patient with ACS is important to rule out complications and possible differential diagnosis.

The following are essential components:

Differential pulse and BP between both arms, which if present may indicate the possibility of aortic dissection

Tachypnoea, pitting leg edema and raised jugular venous pressure with crackles in the base of the lung or only crackles in the base of the lung may indicate either existing heart failure or an acute one secondary to acute myocardial ischemia

A new cardiac murmur may indicate acute valvular insufficiency or rupture interventricular septum

Distant heart sound on auscultation of precordium may indicate acute pericardial effusion secondary to rupture of a free ventricular wall or acute aortic dissection with extension to precordium.

In addition to the above, it is essential to check the vital signs carefully. If the patient has hypotension with acute myocardial ischemia, this may indicate cardiogenic shock. Tachycardia may range from sinus tachycardia to ventricular tachycardia; bradycardia, on the other hand, may range from sinus bradycardia to third-degree heart block.

Differential Diagnosis

There are many critical differential diagnoses when we consider A.C.S. Please look for all in the given table. However, Unstable angina, Acute myocardial infarction, Acute pulmonary embolism, Acute aortic dissection, Tension pneumothorax, Oesophageal rupture (Boerhaave’s syndrome) are the life-threatening ones. We advise you to read these chapters form multiple resources to feel confident.

See the following table:

ACS/Chest Pain Differential Diagnosis

Life threatening

Cardiovascular

Respiratory

Gastrointestinal

Referred pain

Unstable angina

Acute myocardial infarction

Acute pulmonary embolism

Acute aortic dissection

Tension pneumothorax

Oesophageal rupture (Boerhaave’s syndrome)

Stable angina

Acute pericarditis

Myocarditis

Pneumonia

Simple pneumothorax

Gastro-oesophageal reflux

Oesophageal spasm

Sub phrenic abscess / inflammation

Hepatobiliary disease

Acute Complications

The acute complication which we may see in the emergency department includes the following:

Decision Making Process and Reaching The Diagnosis

There are three pillars of diagnosis: history, ECG, and cardiac enzymes.

Clinical features of unstable angina include the following:

Unstable angina differs from stable angina in that the chest pain is usually more intense, easily provoked, more prolonged, more frequent and more severe. All first presentation of angina should be regarded as unstable. In unstable angina typically there is either no ECG changes or non-specific ECG changes, the patient is usually chest pain-free on presentation to the emergency department, and the cardiac enzymes will be normal.

NSTEMI should be diagnosed in any patient whose cardiac enzymes are raised without evidence of ST elevation MI. An NSTEMI does not need to have ECG changes at the time of presentation. The ECG may show the following:

ST-segment depression

The transient ST-segment elevation that resolves spontaneously or after glyceryl trinitrate treatment

T-wave inversion

Evidence of previous myocardial infarction

Left bundle branch block

Minor non-specific changes

The ECG can also be normal. It should not show persistent acute ST-segment elevation.

STEMI (ST-segment elevation MI) is a true cardiac emergency. The criteria of diagnosing ST-segment elevation MI on ECG are: New ST elevation at the J point in at least two contiguous leads of ≥ 2 mm in leads V2–V3 and/or of ≥ 1 mm in other contiguous chest leads or the limb leads.

There are other causes of ST elevation should be known to differentiate it from the ST elevation of myocardial infarction. These are;

Acute pericarditis

Benign early repolarization

Brugada’s Syndrome

Hyperkalemia

Left Bundle Branch Block

Left ventricular aneurysm

Left ventricular hypertrophy

Normal variant

Osborn wave of hypothermia

Prinzmetal’s angina

Ventricular paced rhythm

In general, the difference between unstable angina and NSTEMI/STEMI is an absence of cardiac enzymes abnormalities.

Cardiac enzymes (CKMB, Troponin T or I) are highly sensitive to cardiac muscle injury. Another lab investigation is full blood count, urea, and electrolyte. A chest x-ray may give clues to acute pulmonary congestion or indicate the diagnosis of other conditions like pneumothorax or acute aortic dissection.

Emergency Treatment Options

Initial Stabilization

In typical emergency medicine room, once a patient presents with chest pain suspecting of acute myocardial ischemia should be seen in the monitored area, the patient should remain under continuous cardiac monitoring, HR, BP, and SpO2.

The proper approach will consist of all following:

ECG should be done immediately or within the first 10 minutes by the emergency room staff nurse, which should be interpreted by a senior doctor.

Targeted history of onset of chest pain, associated symptoms and risk factors.

GTN sublingually or spray to relieve chest pain, if chest pain persists after two sublingual GTN tablet, proceed with GTN infusion especially if the patient has concomitant hypertension or heart failure.

IV morphine with anti-emetic if chest pain persisted and titrated according to the response of the patient.

Oral beta blocker if no contraindication within 24 hours.

Definitive treatment depends on which condition within the acute coronary syndrome is diagnosed.

Severe hypertension (blood pressure > 180/ 110 mm Hg)
History of ischaemic stroke >3 months
Presence of dementia
Known intracranial disease that is not an absolute contraindication
Traumatic or prolonged cardiopulmonary resuscitation (CPR) that lasted more than 10 minutes
Major surgery within 3 weeks
Presence of active peptic ulcer
Internal bleeding within the last 2 to 4 weeks
Non-compressible vascular punctures.
Pregnancy
On warfarin therapy
For streptokinase, prior exposure (more than 5 days ago) or history of allergic reaction

In the acute management of acute coronary syndromes, please take note of the following:

If the patient is in shock, always look for precipitating causes:

Do a gentle rectal examination to look for gastrointestinal bleeding.

Is the patient bradycardic? Treat according to ACLS guidelines.

Is the patient tachycardic? Treat according to ACLS guidelines.

Does the patient have a right ventricular infarct?

Do right-sided leads in the presence of ST elevation in II and III and aVF as in inferior AMI (Look for at least 1 mm ST elevation in V4R, V5R, and V6R.

If so, give the fluid challenge of 100-200 ml normal saline over 5 to 10 minutes and assess response.

This can be repeated if the patient does not become breathless and there are no clinical signs of pulmonary edema.

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